Such arrangements are often used to form the absorbent bodies included in diapers, sanitary napkins, incontinence guards and like products, and the bodies often include more than one layer. One problem encountered when air-laying a fibre layer on top of an earlier laid layer is that because of the pressure difference between the interior of the mat-forming hoods which delimit the flows of air-borne fibres, air currents occur at the edges of the hoods, these air streams or air currents having a transversal direction relative to the air-borne fibres and are able to damage or destroy the earlier laid layer. EP-B1-0,292,624 teaches a solution to this problem. This prior document describes two mat-forming hoods which are mounted one immediately after the other, and two vacuum boxes which coact with the hoods. In order to avoid a difference in pressure at the join between the two hoods, the vacuum box of one hood extends beneath the other hood. One drawback with this solution is that the air-laying of fibres beneath one hood is effected under the influence of the subpressure that prevails in two different vacuum boxes, which results in inhomogeneities in the formed layer, and the stream of air-borne fibres is disturbed as a result of the pressure difference occurring in the hood. Another drawback is that the hoods are joined together via a relatively broad gap which equalizes the pressure difference between the hoods in the region of the join.
An object of the present invention is to solve the aforesaid problems in a manner which does not encumber the solution with the drawbacks of the known arrangement.